There are generally two types of dyeing. The first type is semi-permanent dyeing or direct dyeing, which involves dyes capable of giving the hair's natural color a pronounced change. The dyes used are colored and coloring substances that have an affinity for keratin fibers. This type of dyeing fades out after several washes, which may be an inconvenience.
When it is desired to obtain a coloration that is lighter than the original color of the fibers, it is necessary to use, with the direct dyes, at least one oxidizing agent, under alkaline pH conditions. However, these conditions have consequences on the properties of the treated fibers. With time, the fibers become degraded and have a tendency to become coarse, dull, brittle, and difficult to style.
The second type is permanent dyeing or oxidation dyeing. This dyeing is performed with oxidation dye precursors, which are colorless or weakly colored compounds, comprising at least one oxidation base optionally combined with one or more couplers. Once mixed with oxidizing products, at the time of use, the precursors may give rise to colored compounds and dyes via a process of oxidative condensation.
Given the necessary presence of an oxidizing agent in this type of dyeing, the drawbacks mentioned above also occur in this case.
It has recently been found that compositions comprising at least one fluorescent compound represent an advantageous alternative to standard processes using an oxidizing agent. Thus, for dark hair, such as hair with a tone height of less than or equal to 6 (dark blond), such as less than or equal to 4 (chestnut-brown), it can be seen that there are regions for which the curve of reflectance as a function of the wavelength (from 500 to 700 nm) of hair treated with the composition comprising the fluorescent compound is higher than the curve corresponding to untreated hair. Consequently, the hair appears lighter, without the use of an oxidizing agent.
The term “tone” is based on the classification of the natural shades, one tone separating each shade from the shade immediately following or preceding it. This definition and the classification of the natural shades are well known to hairstyling professionals and are published in the book “Sciences des traitements capillaires [Hair treatment sciences]” by Charles Zviak, 1988, published by Masson, pp. 215 and 278. The tone heights range from 1 (black) to 10 (light light blond), one unit corresponding to one tone; the higher the figure, the lighter the shade.
Although such fluorescent compound containing compositions are an advancement in the field, they suffer from the drawbacks of instability upon storage.
Moreover, it would also be desirable to further increase the wash-fastness and shampoo-fastness of the colorations obtained using these compositions.